James Webb vs Hubble: Side-by-side comparisons highlight visual gains
By now you’ve no doubt seen the first batch of images from NASA’s powerful new eye in the sky, the James Webb Space Telescope. But the scope of the achievement can be hard to appreciate without context, so here they are side-by-side with Hubble’s views of the same regions.
The scientific world has been buzzing about the new images from Webb, but you’d be forgiven for quietly thinking, “what’s the big deal?” After all, the public has become used to seeing stunning images of the cosmos over the decades, and at a glance these new ones may not necessarily look much different. It’s not until they’re placed right alongside existing images that the technological advances become startlingly clear.
This structure, which NASA calls the Cosmic Cliffs, is actually the inner edge of NGC 3324, aka the Carina Nebula. Ultraviolet radiation and strong stellar winds from a dying star – located well above the top of frame in this image – is carving these structures into the clouds of dust and gas that are busily forming new stars.
Thanks to its infrared vision, the Webb image on the bottom reveals for the first time many of these baby stars shining through the dust, with the youngest visible as red dots in the darkest parts of the cloud.
Southern Ring Nebula
NGC 3132, better known as the Southern Ring Nebula, is an expanding cloud of gas thrown off by a dying star about 2,500 light-years from Earth. The bright star in the center may look like the culprit, but it’s not – that honor belongs to the much fainter star right next to it.
The left image is the Southern Ring as seen by Hubble in an image released in 1998. The James Webb image on the right provides a clear boost in resolution, bringing the details of the cloud into sharp focus and revealing that the dimmer star is in fact shrouded in its own little cloud of dust.
This cluster of five galaxies, known as Stephan’s Quintet, appears to show five galaxies locked in a cosmic dance. However it should be noted that the leftmost galaxy is actually nowhere near the others – it’s 250 million light-years closer to Earth than the others. It just happens to be in the same patch of sky.
Still, Webb was able to image all five galaxies in much more detail than ever before, peering into their very hearts. There lie supermassive black holes chowing down on dust and gas, visible as bright spots in the center of each galaxy. The new image reveals the flow of gas as the galaxies begin to merge, triggering star formation and sending shockwaves through the system.
This is also Webb’s biggest image, a mosaic of almost 1,000 files collected into an image composed of over 150 million pixels and covering an area about one fifth the diameter of the Moon.
From Webb’s largest image to its smallest, the telescope’s view of the galaxy cluster SMACS 0723 is a slice of sky covering the area of a grain of sand held at arm’s length. This is Webb’s first Deep Field image, staring deeper into space and time than Hubble is capable of.
Hubble’s image on the left shows many faint stars and galaxies, but the Webb image on the right absolutely pops with light, revealing many hidden structures. In particular the redder galaxies are those that are farther away, with the wavelengths of their light stretched towards the red end by the expansion of the universe. As such, many of them fall outside the range of Hubble’s view.
Also much clearer in Webb’s image is the gravitational lens effect, visible as a circular smearing of light in the center of frame. The mass of the cluster is physically warping the fabric of spacetime with its immense gravity, bending and magnifying light from other sources behind it. Webb will be able to use this effect to peer even deeper into space, and as such, further back in time, than any other telescope so far.
But perhaps the most striking context for Webb’s improvement comes from this one-minute video by 10 Questions Visualization. Not only does it highlight how much clearer the new image is, but it zooms out to show the scale of the image in the sky, revealing the truly remarkable density of the new objects.
Of course, these images are just the first few to be released, ushering in what should be decades of stunning sights and discoveries. We can’t wait to see more of the universe through James Webb's powerful eyes.